1. Field of the Invention
The present invention relates to a process for preparing an amorphous and micro/mesoporous silica-alumina gel having a large surface area and a controlled pore size, which is catalytically active in hydrocarbon conversion reactions.
2. Discussion of the Background
Some silica and alumina gels displaying catalytic activity are known in the art. So, e.g., EP-A-160 145 discloses a process for alkylating aromatic hydrocarbons using, as the catalyst, a silica/alumina gel of amorphous character with a diameter of the pores typically of 50-500 .ANG.ngstroms and with a molar silica:alumina ratio typically comprised within the range of from 1:1 to 10:1.
Furthermore, R. M. S. Malton and J. Davidtz in Journal of Catalysis, 60, 156-166 (1979) disclose a process for the synthesis of amorphous silica and alumina catalysts, with a controlled pore volume.
Finally, U.S. Pat. No. 5,049,536 discloses a microporous, x-ray amorphous silica/alumina gel having a surface area of from 500 to 1000 m.sup.2 /g and a pore volume comprised within the range of from 0.3 to 0.6 cm.sup.3 /g. Such a silica and alumina gel, which is catalytically active in hydrocarbon preparation reactions, is typically prepared by hydrolysing a tetra-alkyl ammonium hydroxide, a hydrolysable aluminum compound and a hydrolysable silicon compound and causing the resulting hydrolysis mixture to undergo gelation by operating in an aqueous media and at low temperatures, and then submitting the resulting gel to drying and firing.